A wide variety of relatively sophisticated machines, processes and control strategies are used in connection with site preparation for construction, road building and related projects. In a paving operation, for example, numerous different machines may be used, each of which may be in communication with one another or with a base station where a site manager or computer can monitor progress and make adjustments as necessary. Computer control over various functions of machines used in a paving system is increasingly an effective tool for achieving quality specifications for a particular project. Many machines used in paving are relatively expensive to operate, and contract payments for a particular project are often based on achieving or exceeding contractual requirements. For example, specifications relating to density of the paving material, conditions such as temperature during its application, and in some instances smoothness of the final product are often predefined. Moreover, where specifications are not met, expensive and time-consuming re-work may be required. Accordingly, even modest improvements in paving efficiency or quality are welcomed by the industry.
As mentioned above, smoothness of a mat of paving material may be specified for a particular paving project. It has been discovered that relatively smoother pavement tends to have a longer service life, or at least longer service life at a reasonable level of quality, than relatively rougher pavement. One factor that appears to be responsible for this discrepancy is the relatively high inertial load imparted to bumps, dips or other irregularities in a paved surface by traffic passing over the paved surface. In certain jurisdictions, increased responsibility has been urged upon paving contractors for the long-term durability of roads, parking lots and the like. It will thus be appreciated that paving contractors may complete projects more efficiently, profitably and with greater long-term reliability if they are able to produce a product which is relatively smoother than that possible with conventional techniques.
In preparing a site for paving, building construction, etc., or during the paving process itself, compactors are commonly used to prepare a substrate for bearing loads relating to traffic, structural support, etc. While the end use of a particular substrate may dictate desired compaction specifications for a particular material, in general compaction is achieved by driving, pushing or towing a machine having rotating drums across the substrate of interest to increase its density and uniformity. Compactors are often equipped with vibratory apparatuses to increase and control energy transfer between the compactor and the substrate. It has been observed that different substrates, and similar substrates having different qualities such as moisture level, thickness and other qualities, will tend to respond differently to compactor interaction with the substrate. In recent years, certain manufacturers have experimented with compactor control strategies and compaction progress monitoring, in an attempt to account for differing responses of material to compactor interaction therewith. The response of a material to compactor interaction can affect the smoothness that is ultimately achievable, particularly for a mat of paving material.
Another consideration in attempting to pave a relatively smooth mat is the condition of the subgrade upon which the mat is to be paved. Various machines are known in the art for preparing a subgrade prior to paving a mat of paving material thereon, such as cold planers, recyclers and other reclaiming machines. In general, these machines travel across a region of a work area upon which a mat of material is to be paved, and process the existing material, either by grinding up, mixing and re-depositing the material, or by cutting away a layer of material for disposal elsewhere. While such machines can remove irregularities in a subgrade, resulting in a relatively smoother mat, there is a limit to the extent to which processing subgrade materials is economically practicable, or for that matter even feasible. As a result, paving contractors are often required to pave relatively rough subgrades, but expected to produce relatively smooth results.
U.S. Pat. No. 5,702,2012 Macku et al. is directed to a method for compensating differential compaction in an asphalt paving mat. In Macku et al. an asphalt paver has a compaction compensating system that includes a nominal reference for determining the general profile of underlying terrain, and a compensating ski for determining localized irregularities. A control system alters the thickness of the mat being placed by the paver to compensate for differential compaction of the asphalt material such that a generally planar asphalt paving surface is obtained after compaction. While Macku et al. may have certain applications, under filling and over filling an irregular profile assumes that compactors will interact consistently and uniformly with the entire work area being paved, which is not always the case, or even desirable. Moreover, it can be difficult or impossible to achieve smoothness specifications solely by way of such techniques.